TFTR microwave reflectometer diagnostic

The TFTR (Tokamak Fusion Test Reactor) multichannel X-mode reflectometer system is intended to measure electron density fluctuations at fixed points in the plasma by resolving phase fluctuations in waves reflected from the plasma. The system comprises low-power, high-dynamic-range millimeter-band transceivers two pairs of cylindrical corrugated low-loss overmoded waveguides, remotely controlled beamsteering mirrors, and high-speed data acquisition and control electronics. At present a single 140-GHz channel is operational. Three additional channels, one of which can be frequency stepped, are planned to be operational for the next TFTR run period. These new channels should allow correlation measurements between fluctuations on different density layers. The authors describe the reflectometer instrumentation and design concerns relating to the TFTR environment and discuss the integration of additional channels into the existing single channel system. An example of the measurement capability of the system is presented